Beavers Bring Water Back to Finland’s Drained Wetlands Again

Beavers are emerging as a small but potentially useful counterweight to decades of forestry drainage in southern Finland, according to research examining six decades of landscape change.

The study, carried out in the Evo area, assessed how drainage infrastructure and beaver activity altered forests and peatlands between 1963 and 2023. Researchers combined historical maps and aerial photographs with current geospatial data and long-term field observations.

For forestry operators, landowners and restoration planners, the findings add another dimension to the debate around managing drained peatlands: natural hydrological processes may be able to support restoration in some locations, although they are unlikely to replace active intervention across larger areas.

Forestry drainage has driven long-term hydrological change

The scale of drainage expansion in the study area was significant. Researchers found that the ditch network had almost quadrupled over the 60-year period, while the proportion of drained peatland rose from 23.8% in 1963 to 72.5% in 2023.

Forestry drainage has traditionally been used to remove excess water from peat soils and create conditions considered more suitable for timber production. Over time, however, individual drainage projects can combine to produce broader changes in water movement and wetland conditions.

The Evo findings illustrate that cumulative effect. By comparing modern conditions with historical records, researchers were able to show how substantially the area's hydrology had shifted.

University of Eastern Finland researcher Sonja Kivinen highlighted the value of historical reference points when assessing the extent of landscape change and considering how wetlands could respond to future management and climate pressures.

That longer-term view may be increasingly relevant as forestry businesses and public agencies balance timber production with biodiversity, water management and peatland restoration requirements.

Beaver activity could complement targeted restoration

While drainage remains the dominant influence across the landscape, beavers are creating smaller areas where water is once again being retained.

Researchers recorded 77 active and previously flooded beaver sites across Evo. Together, these sites formed a wetland network covering around 1.4 square kilometres.

The total area is modest compared with the extent of drained land, but the local impacts can be substantial. Beaver dams slow water movement and can raise water levels around streams, lakes and other watercourses, creating ponds and wetland habitats without the excavation or construction associated with conventional restoration projects.

Researchers from the University of Helsinki suggest this process could have a role in selected restoration strategies. Rather than viewing beavers as a replacement for engineered measures, land managers could consider where their activity might support wider hydrological objectives.

There are also potential implications beyond habitat creation. International research has linked headwater wetlands with increased water retention and slower downstream release, characteristics that can be relevant during periods of heavy rainfall or drought.

The Finnish study does not indicate that beavers can reverse landscape-scale drainage. Decades of ditch construction have altered a much larger area than beaver flooding currently affects.

Instead, the research points to a more practical role: beaver-created wetlands could become one component of a wider restoration toolkit, particularly in locations where natural flooding aligns with land-use and water-management objectives.

For forestry companies, landowners and public bodies, the next step is likely to be identifying where those natural processes provide measurable ecological and hydrological value, and where conventional restoration will still be required.